We can also use probability trees to find the probabilities. Notice that we get the same result whether we use the first column for cars or for stereos:
Example 2 In order to test a new car, an automobile manufacturer wants to select 4 employees to test drive the car for one year. If 12 management and 8 union employees volunteer to be test drivers and the selection is made at random, what is the probability that at least 1 union employee is selected?
The sample space is the set of all possible sets of 4 drivers taken from these 20 volunteers.